In state of the art UMTS, after channel decoding, the data are collected as (hard) bits into so-called transport blocks (TB). The contents of these transport blocks are compared with the attached cyclic redundancy check (CRC) fields (which can have a size between 8 and 24 bits) in order to check whether the transport block is corrupted or not. Thereupon, the CRC field is deleted, and the information whether the CRC was “good” or “bad” is contained in a one-bit indicator called CRCI. Then, the transport blocks belonging to one channel's transmission timing interval (TTI) or to the TTI of one set of coordinated channels are collected into an uplink frame protocol (FP) data frame together with their corresponding CRCIs, regardless whether the data is corrupted or not.
In each FP frame, for each transport channel, the radio network controller (RNC) receives a transport format indicator (TFI), which indicates the actual number of transport blocks in the transport channel and their size (all transport blocks in a transport channel are of equal size). The TFI may change from one FP frame to the next frame containing data of the same transport channel.
Via fixed links, e.g. between a base station and an RNC, the complete uplink FP data frames are sent to the RNC. In UMTS (or any other CDMA system), one connection may involve more than one Node B, in which case the connection is indicated to be in “soft handover” state. At the RNC, for a connection being in “soft handover” state, uplink transport blocks come in parallel from each Node B involved. Based on quality estimate (QE) and CRCI information, “selective combining” takes place, comprising the selection of one transport block while rejecting all other transport blocks for the some transport channel and the same transport time interval (TTI).
A simplified FP data frame of the state of the art is shown in FIG. 4. The data frame starts with a data frame header DFH. This is followed by a number of fixed size transport format indicators TFIs for each dedicated channel DCH. Then the transport blocks TBs (hard bits) for each dedicated channel DCH follow, the size of which depends on the TFIs. Fixed size quality estimate QE information is provided before the cyclic redundancy check indicators CRCIs of each dedicated channel DCH, where the size of the cyclic redundancy check indicators CRCIs of each dedicated channel DCH also depends on the transport format indicators TFIs of the respective DCH.
In the state-of-the-art scheme, for each single transport block, the RNC receives the user data (either error-free or knowingly corrupted) and the one-bit CRCI “good” or “bad” information.
This means that, although the state of the art provides for a silent mode, which suppresses complete data frames to be transmitted on the interface when during a transmission time interval no data is available for a given transport channel, when data frames are transmitted, they are always transmitted in full length, containing even in full length those transport blocks known to be disturbed. In many cases a receiver rejects disturbed data and requests for repeated transmission. However, the unnecessary transmission of the corrupted transport blocks inevitably occupies interface resources and thus, it reduces the effective data rate of the interface between a base station and a network controller.